The stun applies to the first ability that lands when the stun is available. If you cast Disintegrate followed by Incinerate while the stun is available and Disintegrate is in the air, the stun will apply to Incinerate.

The stun will not be consumed if the target of Disintegrate becomes untargetable or the projectile is destroyed by Wind Wall.

First Cast:Annie summons Tibbers to the target location in a burst of flame, dealing magic damage to all nearby enemies enemies. He then remains on the field as a controllable minion for up to 45 seconds.

Initial Magic Damage: 175 / 300 / 425 (+ 80% AP)

Second Cast: While Tibbers is active, Summon: Tibbers can be used to move him to the target location.

Tibbers deals magic damage with his basic attacks, and is also surrounded by a flaming aura which deals magic damage every second to nearby enemies.